1. Field of the Invention
This invention relates to a multi-beam photoelectric sensor and its mount.
2. Discussion of the Related Art
Multi-beam photoelectric sensors disclosed in U.S. Pat. No. 6,166,371, International Publication No. WO 00/54077 and Japanese Patent Laid-Open Publication No. 2000-251595 each include units of paired light emitters and photo detectors to make a protective fence, typically called a light curtain, of a desired size by using one or more units of light emitters and photo detectors. Multi-beam photoelectric sensors of this type are widely used for prohibiting intrusion of any part of a worker""s body or any other object into a prohibited zone around a work area with a machine tool, press machine, etc.
Multi-beam photoelectric sensors typically need positioning of light emitters and photo detectors in an opposed relation upon their initial setup, and need adjustment of optical axes between light emitters and photo detectors. Adjustment of optical axes includes rotation of light emitters and/or photo detectors about their own axes. Light emitters and/or photo detectors can be adjusted in rotational orientation by appropriate amounts of rotation.
FIG. 1 and FIG. 2 show examples of existing mount for multi-beam photoelectric sensors. In each of these examples, the multi-beam photoelectric sensor 1 includes a plurality of through holes 3 aligned in a single row in equal intervals on the light emitting or detecting surface that is the front surface of a body 2. The multi-beam photoelectric sensor 1 exchanges equally spaced light beams through these holes.
The multi-beam photoelectric sensor 1 is fixed on a support (not shown), which is an external structure like a frame of a press machine, via a bracket 4. In the example of FIG. 1, the bracket 4 includes a base member 5 and a plate member 6. The plate member 6 is firmly fixed to the base member 5 by bolts 7. The bracket 4 defines a shaft hole between the base member 5 and the plate member 6 to receive a shaft 17 having a circular section and axially extending from top and bottom ends of the sensor body 2. When the bolts 7 are rotated in the fastening direction, the multi-beam photoelectric sensor 1 is fixed to the bracket 4 and prevented from relative rotation. When the bolts 7 are loosened, the multi-beam photoelectric sensor 1 can rotate about the axis.
In the example of FIG. 2, the bracket 4 is a member having an L-shaped section, which includes a base portion 8 for engagement with the support and a sensor mount portion 9 extending perpendicularly to the base portion 8. The base portion 8 has elongate holes 10 longer in the axial direction of the multi-beam photoelectric sensor 1 to enable adjustment of the multi-beam photoelectric sensor 1 in its axial position.
The sensor mount portion 9 of the bracket 4 has a round hole 11 for receiving the shaft 17 of the sensor 1, and a plurality of elongated arcuate holes about the round hole 11. The sensor 1 is fixed to the bracket 4 by bolts (not shown) inserted through the arcuate holes 12.
In the existing example shown in FIG. 2, when the bolts in the arcuate holes 12 are rotated in the releasing direction, the sensor 1 is permitted to rotate about its axis. When the bolts are rotated in the fastening direction, the sensor 1 is fixed no to be rotatable about the axis. That is, the sensor 1 is fixed in rotational orientation.
In any of the existing examples shown in FIGS. 1 and 2, when a plurality of multi-beam photoelectric sensors 1 are used together in straight or angled connection to make a large light curtain, it is practically impossible to make a light curtain without a large gap between the nearest light beams of every two adjacent sensors 1, 1. That is, it is practically impossible to place the adjacent sensors 1, 1 such that the pitch between the extreme light beam of one sensor 1 and the nearest light beam of another sensor 1 equals the pitch of the light beams within each sensor 1.
Additionally, the existing example of FIG. 2 involves the problem that the adjustable extent of the sensor 1 in its rotating direction is substantially limited by the length of each arcuate hole 12. Therefore, the sensor 1 can be adjusted in rotational orientation only within a limited range.
It is therefore an object of the invention to provide a multi-beam photoelectric sensor and its mount of a scheme different from existing ones.
A further object of the invention is to provide a multi-beam photoelectric sensor and its mount that are capable of connecting a plurality of multi-beam photoelectric sensors substantially in direct contact and suitable for placing a plurality of multi-beam photoelectric sensors such that the pitch of light beams between adjacent multi-beam photoelectric sensors equals the pitch of light beams within each multi-beam photoelectric sensor.
A still further object of the invention is to provide a multi-beam photoelectric sensor and its mount that are designed to facilitate enlargement of the rotatable angle of the multi-beam photoelectric sensor, that is, the adjustable extent of its rotational orientation.
Those objects of the invention can be accomplished by various aspects of the invention.
According to an aspect of the invention, there is provided a multi-beam photoelectric sensor comprising:
a light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing;
a photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing;
a cable connected to at least one of lengthwise ends of the casing of the light emitter to supply an electric power and/or transmit a signal;
a cable connected to at least one of lengthwise ends of the casing of the photo detector to supply an electric power and/or transmit a signal;
a light emitter mounting means for mounting the casing of the light emitter to a support, said light emitter mounting means being positioned on a back surface of the casing of the light emitter opposite from a light emitting surface from which the light emitting elements emit light beams; and
a photo detector mounting means for mounting the casing of the photo detector to a support, said photo detector mounting means being positioned on a back surface of the casing of the photo detector opposite from a photo-detecting surface where the photo detector elements receive light beams.
In the multi-beam photoelectric sensor summarized above, at least one of the light emitter mounting means and the photo detector mounting means preferably includes means for adjusting the corresponding elongate casing in rotational angular position about a lengthwise axis thereof. Adjustment of optical axes is to adjust relative orientations of the light emitter and the photo detector, and it can be accomplished by adjusting at least one of the light emitter and the photo detector in its orientation.
According to another aspect of the invention, there is provided a multi-beam photoelectric sensor comprising:
a light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing;
a photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing;
a light emitter mounting means for mounting the casing of the light emitter to a support, said light emitter mounting means being positioned on a back surface of the casing of the light emitter opposite from a light emitting surface from which the light emitting elements emit light beams;
a photo detector mounting means for mounting the casing of the photo detector to a support, said photo detector mounting means being positioned on a back surface of the casing of the photo detector opposite from a photo-detecting surface where the photo detector elements receive light beams;
said light emitter mounting means and said photo detector mounting means including rotational position adjusting means for adjusting rotational angular positions of the light emitter and the photo detector; and
said light emitter mounting means and said photo detector mounting means including lengthwise position adjusting means for adjusting lengthwise positions of the light emitter and the photo detector.
According to another aspect of the invention, there is provided a mount for mounting one of a light emitter and a photo detector of a multi-beam photoelectric sensor to a support, said light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing and said photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing, comprising:
said casing having an arcuate portion which projects outwardly at least around the back surface of the circumferential surface of the casing excluding the front surface of the casing;
said mount including a first member and a second member positioned to hold the arcuate portion of the casing therebetween; and
said first member and said second member including fastening means capable of tightly joining each other.
According to another aspect of the invention, there is provided a mount for mounting one of a light emitter and a photo detector of a multi-beam photoelectric sensor to a support, said light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing, and said photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing, comprising:
said casing having an arcuate portion which extends perpendicularly to the lengthwise direction of the casing, said arcuate portion having opposite side surfaces which define the arcuate portion in the lengthwise direction of the casing and form first slanting surfaces sloping down toward the inner circumferential surface thereof;
said mount having a rectangular opening which partly receives the arcuate portion of the multi-beam photoelectric sensor, opposite side surfaces of the rectangular opening being second slanting surfaces slanted with a complementary angle with the first slanting surfaces of the arcuate portion; and
said mount having a stopper for urging the arcuate portion from the back surface thereof.
According to another aspect of the invention, there is provided a mount for mounting one of a light emitter and a photo detector of a multi-beam photoelectric sensor to a support, said light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing, and said photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing, comprising:
a first member which can be fixed to the support;
a second member which is positioned behind the back surface of the casing and can be fixed to the support; and
a third member which can be affixed to the casing to extend in an arcuate form around the back surface of the casing,
wherein opposite side surfaces of the arcuate third member are first slanting surfaces sloping down toward the inner circumferential surface thereof,
wherein the second member has a rectangular opening for partly receiving the arcuate third member, opposed sidewalls defining the rectangular opening are second slanting surfaces slanted by a complementary angle with the first slanting surfaces, and
wherein the first member includes a stopper which exerts an urging force to the back surface of the arcuate third member, and
wherein the casing can be adjusted in rotational angle about a lengthwise axis thereof by reducing the urging force of the stopper to the third member even after the casing is fixed to the external structure by the mount.
According to another aspect of the invention, there is provided a mount for mounting one of a light emitter and a photo detector of a multi-beam photoelectric sensor to a support, said light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing, the elongate casing having lengthwise grooves in opposite side surfaces thereof, and said photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing, the elongate casing having lengthwise grooves in opposite side surfaces thereof, comprising:
a base member which can be fixed to the support;
an elongate member extending around the back surface of the casing perpendicularly to the lengthwise direction of the casing;
guide means formed as a part of the base member to engage with the elongate member and guide rotation of the casing about a lengthwise axis thereof;
a stopper member supported by the base member to engage with the elongate member; and
an operation member capable of releasing the engagement of the stopper with the elongate member,
wherein the casing can be adjusted in rotational position by manually operating the operation member and thereby reducing the engagement force between the stopper member and the elongate member.
According to another aspect of the invention, there is provided a multi-beam photoelectric sensor comprising:
a light emitter having a plurality of light emitting elements contained in an elongate casing and aligned in the lengthwise direction of the casing in equal intervals;
a photo detector having a plurality of photo detector elements contained in an elongate casing and aligned in the lengthwise direction of the casing in substantially the same equal intervals as those of the light emitting elements;
a light emitter mounting means positioned within the full length of the light emitter casing for fixing the light emitter casing to an external structure; and
a photo detector mounting means within the full length of the casing for fixing the photo detector casing to an external structure.
These and other objects and advantages of the invention will appear clearly from the following description of preferred embodiments.